Tuesday, September 25, 2012

When I saw the tweet, I thought it was another prank. The tweet had a link to a PDF file about the high levels of radioactive cesium in one tree in the yard of a resident in Abiko City located on the west corridor of Chiba with relatively high radiation contamination. The web address of the link indicated it was from the city government, but there was no mention of the city in the document. So I went to the homepage of Abiko City, and see if I could find the same document from the links at the homepage.

The apple in question was brought by a city resident and tested on August 20, 2012 using the city's NaI scintillation survey meter. As the number was extraordinarily high, the city sent officials to the resident's home to collect more samples and tested them using the germanium semiconductor detector to be more precise. The result using the germanium detector was even higher.

The city says it was cautious in releasing the information, for fear that it might generate "baseless rumors". The amount of radioactive cesium in the apples, leaves and branches from the particular tree was extremely high, and couldn't be explained by comparing it to the samples taken in the same yard and in the neighborhood.

The apple tree is an ornamental apple tree, though the fruit is edible. It was planted by the resident of the house about 6 years ago when the resident moved in. The resident brought the apple to the city's testing lab, and the test was conducted on August 20, 2012.

The test results (radioactive cesium total):

Apple

Using the city's NaI scintillation survey meter: 1,500 Bq/kg

Using the survey meter at the Board of Education: 1,300 Bq/kg

Using the germanium semiconductor detector: 1,660 Bq/kg

Soil where the apple tree was planted

Using the survey meter at the Board of Education: 2,900 Bq/kg

Leaves and branches of the particular apple tree

City's test: over 10,000 Bq/kg

Leaves and branches of other trees in the same yard, including a different variety of apple tree right next to the highly contaminated apple tree

City's test: 48 to 111 Bq/kg

Apples from the same apple variety that neighbors grow

City's test: less than 100 Bq/kg

The city asked the Ministry of Agriculture's Horticulture Bureau and a government laboratory to investigate, but they couldn't come up with a plausible explanation why this peculiar contamination happened. The city also asked the National Institute of Radiological Sciences and the Central Research Institute of Electric Power Industry

The city decided to release the information with a caveat that the apple was from a home garden and not commercially sold, so that people wouldn't panic unnecessarily.

So no one knows why this one particular apple tree ended up with such a high level of contamination and not the tree right next to it. But aren't scientists curious?

At least, it proves that sample testing is very efficient, because all apples from the same yard are contaminated alike... eh eh eh

Since it's an ornamental apple, it was probably coated with the setagaya radioactive paint frome before ? But seeing how shops in here only sell shiny fruits, I wouldn't be surprised if people found out similar results. That is, if they were looking.

Seriously now, I agree with the smoking gun comment, and here is what my supermarket [within tokyo 23] has to sell :

. cucumbers from fukushima [used to have kyoto for 50% premium, not anymore]. eggplant from tochigi [used to have a kansai variety, no more]. tomatoes from fukushima [used to have hokkaido, no more]. nashi -a kind of pear- from fukushima. carrots from chiba [hokkaido before]. peaches, fukushima of course

Actually, the only products still advertised as western japan origin are eggs, chestnuts, milk, yoghurt and rice. I suspect someone claimed somewhere on TV that fruits/vegetable contamination is over now... But I don't watch TV so dunno. And most of the frozen vegetables/fruits are from china...

It's pretty clear they are desperately trying to differentiate between affected and not affected. But as Beppe said, radiation doesn't discriminate. It's beyond ridiculous that humans seriously think they can control and get around the contamination.

It's like constantly narrowly dodging oncoming bullets in the f'n Matrix. Except, this is reality and none of us is "the chosen one".

No strange bottles leaking under that tree ?Does the radiation bear the sign of Fuku ? No data given except becquerels.Anyway JAnonymous in Tokyo 23 you are plain right, that's the problem.I am a bit better, but not much, when I stay in the center of Tokyo prefecture.And when we find food from almost clean locations, it is at a dear price.

laprimavera, it is clearly a hotspot of some kind. Maybe the yard is sloped and this tree is at the bottom. Maybe something else entirely, like the suggested radium bottles. There are ditches on the sides of roads in the exclusion zone around Chernobyl which are still deadly.

I am interested in another thing though. Why did the resident bring the apples he wasn't eating for rad testing?

A typical banana has .5 g of radioactive potassium. A typical banana has a rate of 31 Bq/gram due to this (see ref below). Multiplying by 1000 grams/kg this gives a corresponding average banana a measurement of 31000 Bq/kg.

So the average banana can be expected to be 18 2/3 more than this apple. Which backs up what I’ve been saying all along - you can measure anything you want throughout Japan or near any other nuclear site - but without references on what is expected to be naturally occurring no one can tell if anything is really an issue or not. By the way just caculating the .5g of radioactive potassium in the banana gives you a dosage of ~.1 microseiverts. (5.02 nSv/Bq X 31 Bq/g X .5 g = 78nSv ~ .1 uSv)

For those who are more familiar with the older terms 1 mRem = 10 uSv so .1 uSv/banana X 1 mRem/10 uSv = .01 mRem/banana)

Brazil nuts by the way can be as much as as 4 times higher than the bananas due to natural radon.

Ref: http://health.phys.iit.edu/extended_archive/9503/msg00074.html (gary mansfield, Lawrence Livermore National Laboratory, the University of California)

You can also go to http://en.wikipedia.org/wiki/Banana_equivalent_dose for additional information orhttp://rehs.rutgers.edu/online_training/xray_train/Five.htmlhttp://www.tenorm.com/bkgrnd.htmhttp://web.princeton.edu/sites/ehs/osradtraining/backgroundradiation/background.htm#tophttp://en.wikipedia.org/wiki/Background_radiationhttp://www.civildefensemuseum.com/southrad/conversion.html

And a note to Janon- you can buy cheap veggies from outside the hot zone at costco. I suspect you should be able to find them (altough at higher prices) at National Azabu in town and at various stores near the American school in Chofu/Musashi Sakai. If that fails, try the foreign buyers club at fbcusa .com.

Costco is a good tip ; a Japaneese lady drove us there twice, in Chofu, it is cheap and properly checked. Very funny, as we are far from XXL, and used to japanese or mediterranean diet, and there you buy cheese per kilo, spaghettis per 5 kilo, have pizzas as large as a table and so on... Worth the trip if you have a car and a hungry familly to feed.

This contaminated apple contains 1660Bq/kg, hence this apple is 13 times more radioactive than bananas (per kg). A banana weights about half an apple, hence it takes 26 bananas to match this apple dose rate.

Furthermore, if we compare apples to apples, an apple contains .2gr of potassium and weights 250 gr so 1 kg of apples contains .2*1000/250*31 = 25Bq of potassum. It takes therefore 1660/25=66 clean apples to match the dose rate of the contaminated one.

But there is more: Cesium has a biological half life of 70 days whereas potassium is 30 days; the internal exposure caused by this apple is therefore 70/30*66=154 times larger than the exposure of a clean apple.

Your comparison describes clean bananas as 18 times higher than this apple; my comparison evaluates clean apple as 154 times lower than the contaminated apple so we are apart by nearly 2800 times.

Readers should also note that this kind of estimates are still very approximate (aside from any mistakes I might have made, I am not a professional in the field). Some discussion can be found under the Criticism section at http://en.wikipedia.org/wiki/Banana_equivalent_dose.

Furthermore the above calculation does not take into account differences in terms of site of accumulation of cesium vs. potassium.

I live in Abiko, actually, and this kind of stuff doesn't surprise me at all. Shortly after the accident I found a clump of dirt reading over 6uSv/hr whereas the reading all around it was around 0.2-0.3. And yes, the dirt was reading 6 microsieverts, not 0.6. When the fallout hit all over Fukushima and elsewhere it fell in many ways like a sprinkling of sparkles on a Christmas cookie. It's gonna naturally be thicker in places than others. Just the luck of the draw.

According to Japan Times online "Cesium contamination in food appears to be on wane"

http://www.japantimes.co.jp/text/nn20120925i1.html

Staff writer Mizuho Aoki goes as far as unearthing stuff like "when someone is exposed to a cumulative dose of 100 millisieverts, the risk of dying from cancer goes up by 0.5 percent, according to many scientists" and forgets to mention than according to Japanese law exposure from manmade sources is required to be below 1mSv/yr for the general population.

By the way, JT allows you to send them comments, see the link at the bottom of the storyBeppe

According to the document linked by Primavera-san the city of Abiko decided to add statements like "grown privately" and "non commercialized" in order to prevent "damaging rumors" (風評被害).Now, who would be damaged by the rumors? Who would be damaged from eating equivalently contaminated produce?Beppe

Hey Professor Banana you really flubbed the radioactive Banana equation. One banana doesn't weight anywhere near 1000 grams! First off I'm assuming you don't eat the skin with your banana and without the skin the average banana runs 90-140 grams not 1000. In addition comparing K40 to Cs137 is comparing apples to bananas if Cs137 was "safe" as a food additive it wouldn't be considered nuclear waste and we wouldn't be going to great expense to contain it. Oh, and then there is this:

The human body maintains relatively tight homeostatic control over potassium levels. This means that the consumption of foods containing large amounts of potassium will not increase the body’s potassium content. As such, eating foods like bananas does not increase your annual radiation dose.

for those in tokyo, joining a food coop like seikatsu club would offer some protection, as they do test foods and announce the results. I'm not sure what their BQ/K limit is though. there is another coop from western japan, Alter, that aims for less than 1bq/k. we ordered from Alter when we were in Yokohama this summer, but it is expensive.

They know why one spot is hot while others are not but if they told people fallout doesn't spread in a uniform manner intelligent people would start thinking the small sample testing they are doing on food and land is useless. This is just more proof that radiation doesn't follow the nice neat circles the "experts" draw it is more like a shotgun blast that follows the turbulent winds.

Look, they've had 26 year to conduct research on the fallout effects and physics of Chernobyl but much of it remains a "mystery" because the people in power don't want to know. I would think since the hot apple tree is a different type than the lesser contaminated variety that may have something to do with how much dose it absorbed.

"Fallout from Chernobyl remains a poorly-investigated hazard for the environment a quarter of a century after the disaster, say experts."

"Contamination, even in the notorious exclusion zone, is not uniform.

Some areas are quite clean. But a few hundred meters (yards) away, there can be "hot spots" -- determined by the winds and rain that deposited the particles, or the leaves that trapped them -- where radiation is far higher."

About my coverage of Japan Earthquake of March 11

I am Japanese, and I not only read Japanese news sources for information on earthquake and the Fukushima Nuke Plant but also watch press conferences via the Internet when I can and summarize my findings, adding my observations.

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